You will need some longer days to trigger laying, if they haven't been through the winter. Their laying hormones and brooding hormones, I've read, are connected...the bird needs to feel there is enough warmth, and food, to warrant bringing in chicks to feed.
You might want to increase the protein intake, make sure they have quiet, dark, and cushy dry nests, and leave some fake eggs for a good clutch. The hormones are kicked in by warmth (simulating spring time) and the pressure of eggs on their breast (simulating laying a full clutch).
While I have had my very broody prone Silkie brood through any and all seasons, my large fowl broodies generally go broody around May/June. That is a common time.
Hopefully as the days lengthen and warm, encouraging the hormones, and maybe a few enticements, your birds will decide to brood.
Lady of McCamley
Thanks! So looks like I'm in for a looooong wait.... While the days may be lengthening, they're not warming up anytime in the foreseeable future
